Position-measuring devices are described in PCT International Published Patent Application No. WO 02/23131, for example. Besides a measuring graduation, developed, for example, as a linear incident light scale, it includes a scanning unit that is displaceable with respect to it in at least one measuring direction. On the side of the scanning unit, besides a scanning grating, several optoelectronic detector elements, among other things, there is arranged also at least one optical reflector element in the form of a retroreflector. A back reflection takes place via the retroreflector of the partial beam of rays reflected in the first place by the measuring graduation, in the direction of the measuring graduation. There, the partial beam of rays is then subsequently reflected a second time, before finally interfering partial beams of rays reach the detectors, and in that place generate scanning signals that are modulated as a function of displacement. In the position-measuring device of this type, the reflector element is arranged as a roof prism having optical retroreflector functionality. Additional position-measuring devices having optical reflector elements developed as prism-type retroreflector elements are described, for example, in European Published Patent Application No. 0 387 520 and European Published Patent Application No. 1 347 271.
The reflector elements based on various prism variants, conventional for position-measuring devices, represent component parts that are relatively costly to manufacture. In addition, these component elements take up a great deal of space, and this results in an undesired enlargement of the scanning unit.